A comprehensive, randomized clinical trial emphasizing early diagnosis as the key variable has been underway since 1985. Nutritional status has been assessed using height and weight measurements and biochemical methods. The results have demonstrated significant benefits in the screened (early diagnosis) group. We are now focusing on the effect of early diagnosis of CF on pulmonary outcome. Pulmonary status is measured using chest radiographs, chest scans using high resolution computerized tomography, and pulmonary function tests. Other factors that we are looking at include risk factors for the acquisition of respiratory pathogens such as Pseudomonas aeruginosa, quality of life and cognitive function of children with CF who underwent early versus delayed diagnosis, as well as the cost effectiveness of screening and the costs of diagnosis and treatment of CF throughout childhood.